An apparatus of the type referred to above is described in U.S. Pat. No. 4,489,690. To optimize the torque delivered by an internal combustion engine or the specific fuel consumption, a test signal generator for varying the amount of fuel metered and a sensor for detecting the quantity to be optimized are utilized. On the basis of a torque signal, the maximum power or the minimum specific fuel consumption are determined depending on the load range of the internal combustion engine. While such arrangements have proven well in practice, further developments and improvements are still possible, particularly with a view to more stringent emission control legislation and efforts to lower the fuel consumption of internal combustion engines.
Thus, for example, investigations have shown that the individual cylinders of an internal combustion engine are normally operated with different air-fuel ratios. The reasons for this are, among others, differences in intake ducting and injection valves which are not fully identical.